In recent high-speed, high-density signal transmission between electronic devices or between circuit boards, a customary transmission technique through electric wirings has began to reveal limitations in realization of high speed and high density signal transmission, because mutual interference between signals and electromagnetic noise from surroundings constitute barriers. In order to overcome such limitations, a technology for optically connecting between electronic devices or between circuit boards, a so-called optical interconnection, is being examined. A flexible optical waveguide having satisfactory flexibility has been considered to be suitable as an optical path, because this can be easily connected with a device or substrate (board) and has satisfactory handleability.
Customary flexible optical waveguides have employed epoxy compounds. Such epoxy compounds, however, show poor polymerization reactivity (curability), high skin irritancy, and high toxicity and thereby have disadvantages in handleability and safety, although they give cured objects which excel in chemical resistance and adhesion. Independently, there has been an attempt to adopt polyimides to flexible optical waveguides, but the attempt has proved as being limited, because the polyimides should be prepared at high temperatures; they are significantly restricted in solvents when they are handled as polymers to form polymer solutions; and they are very expensive.
Japanese Unexamined Patent Application Publication (JP-A) No. H10-25262 and Japanese Unexamined Patent Application Publication (JP-A) No. 2003-73321 disclose some alicyclic vinyl ether compounds as polymerizable compounds. These compounds show low skin irritation potential and thereby have improved safety, but are still insufficient in thermal stability and optical transparency and need improvements.
Japanese Unexamined Patent Application Publication (JP-A) No. H10-316670 discloses a vinyl ether compound having an oxetane ring in the molecule. This compound, however, is not always satisfactory, because the compound, when having a long glycol chain, gives a cured object having flexibility but showing insufficient thermal stability and optical transparency; and the compound, when having a short glycol chain, gives a cured object having insufficient flexibility. Japanese Unexamined Patent Application Publication (JP-A) No. H07-233112 and Japanese Unexamined Patent Application Publication (JP-A) No. H11-171967 disclose vinyl ether compounds each including, in the molecule, an alicyclic epoxy group composed of a cyclohexane ring and an oxirane ring bonded to each other. The compounds, however, show poor flexibility and are difficult to be adopted to flexible optical waveguides and other uses where flexibility is required, although they excel in thermal stability, optical transparency, and curing rate.
Japanese Unexamined Patent Application Publication (JP-A) No. 2008-266308 discloses a vinyl ether compound containing an oxetane ring. This compound, however, has poor flexibility and is hardly applicable to flexible optical waveguides and other fields where flexibility is required, although the compound excels in thermal stability, optical transparency, and curing rate. Japanese Unexamined Patent Application Publication (JP-A) No. 2006-232988 discloses an example in which a cyclic ether compound containing a vinyl ether structure is added with an epoxidized polybutadiene having hydroxyl groups at both terminals. The resulting compound is, however, inferior in thermal stability and optical transparency to vinyl ethers further having a reactive cyclic ether in the same molecule, because the compound has only vinyl ether as a reactive group.